RBM4B is an RNA-binding protein encoded on chromosome 11 that belongs to the RBM4 family of proteins. RBM4B contains two RNA recognition motifs and a retroviral-type zinc finger domain, similar to its paralog RBM4a 1. While RBM4a is widely expressed across tissues, RBM4b shows restricted expression primarily in kidney and liver, functioning as a nuclear phosphoprotein with a half-life of approximately 4.5 hours 1. According to functional predictions, RBM4B is required for translational activation of PER1 mRNA in response to circadian clock signaling through direct binding to the 3'-UTR of PER1 mRNA. RBM4B participates in circadian rhythm regulation and entrainment of the circadian clock by photoperiod, in addition to roles in translation regulation and alternative mRNA splicing. Genetically, RBM4B represents a pleiotropic locus shared between anxiety disorders and autoimmune diseases including rheumatoid arthritis, Crohn's disease, ulcerative colitis, psoriasis, and Sjögren's syndrome, suggesting involvement in inflammation and adaptive immunity pathways 2. In pancreatic cancer, RBM4B was identified as a component of a circadian clock-related prognostic gene signature associated with patient stratification and immune infiltration patterns, with high-risk patients showing reduced CD8+ T cells and B cells 3. The functional significance of RBM4B in circadian biology and immune regulation warrants further investigation.